How to check RPM package dependencies on Fedora, CentOS or RHEL

A typical RPM package on Red Hat-based systems requires all its dependent packages be installed to function properly. For end users, the complexity of such RPM dependency is hidden by package managers (e.g., yum or DNF) during package install/upgrade/removal process. However, if you are a sysadmin or a RPM maintainer, you need to be well-versed […]
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How to analyze Squid logs with SARG log analyzer on CentOS

In a previous tutorial, we show how to configure a transparent proxy with Squid on CentOS. Squid provides many useful features, but analyzing a raw Squid log file is not straightfoward. For example, how could you analyze the time stamps and the number of hits in the following Squid log? 1404788984.429 1162 172.17.1.23 TCP_MISS/302 436 […]
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How to set up Squid as a transparent web proxy on CentOS or RHEL

In a previous tutorial, we have seen the method of creating a gateway using iptables. This tutorial will focus on turning the gateway into a transparent proxy server. A proxy is called “transparent” when clients are not aware that their requests are processed through the proxy. There are several benefits of using a transparent proxy. […]
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How to run Docker containers on CentOS or Fedora

Lately Docker has emerged as a key technology for deploying applications in the cloud environment. Compared to traditional hardware virtualization, Docker-based container sandbox provides a number of advantages for application deployment environment, such as lightweight isolation, deployment portability, ease of maintenance, etc. Now Red Hat is steering community efforts in streamlining the management and deployment […]
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How to set up a primary DNS server using CentOS

Any operational domain has at least two DNS servers, one being called a primary name server (ns1), and the other a secondary name server (ns2). These servers are typically operated for DNS failover: If one server goes down, the other server becomes an active DNS server. More sophisticated failover mechanisms involving load balancers, firewalls and […]
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How to set up a transparent HTTPS filtering proxy on CentOS

HTTPS protocol is used more and more in today’s web. While this may be good for privacy, it leaves modern network administrator without any means to prevent questionable or adult contents from entering his/her network. Previously it was assumed that this problem does not have a decent solution. Our how-to guide will try to prove […]
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How to set up MailScanner, Clam Antivirus and SpamAssassin in CentOS mail server

In the world of mail servers, MailScanner is one of the best open source software for virus scanning and spam detection. MailScanner relies on pre-installed anti-virus and anti-spam software to check incoming and outgoing emails for malicious content or patterns of spamming. This makes sure that the mail server does not participate in the distribution […]
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How to configure SNMPv3 in Ubuntu, CentOS and Cisco

Simple Network Management Protocol (SNMP) is a widely used protocol for gathering information about what is going on within a device. For example, CPU and RAM usage, load on a server, traffic status in a network interface, and many other interesting properties of a device can be queried using SNMP. Currently, three versions of SNMP […]
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